Cardiovascular System

1. Cardiovascular SystemCardiovascular System

2. The Blood VesselsThe Blood Vessels
The The cardiovascular systemcardiovascular system has three has three
types of blood vessels:types of blood vessels:
ArteriesArteries (and (and arteriolesarterioles) – carry blood ) – carry blood
away from the heartaway from the heart
CapillariesCapillaries – where nutrient and gas – where nutrient and gas
exchange occurexchange occur
VeinsVeins (and (and venulesvenules) – carry blood toward ) – carry blood toward
the heart.the heart.

3. Blood vesselsBlood vessels

4. The ArteriesThe Arteries
ArteriesArteries and arterioles take blood and arterioles take blood
away from the heart. away from the heart.
The largest artery is the The largest artery is the aortaaorta. .
The middle layer of an artery wall The middle layer of an artery wall
consists of consists of smooth musclesmooth muscle that can that can
constrict to regulate blood flow and constrict to regulate blood flow and
blood pressure. blood pressure.
ArteriolesArterioles can constrict or dilate, can constrict or dilate,
changing blood pressure.changing blood pressure.

5. The CapillariesThe Capillaries
CapillariesCapillaries have walls only one cell thick to have walls only one cell thick to
allow exchange of gases and nutrients allow exchange of gases and nutrients
with tissue fluid. with tissue fluid.
Capillary beds are present in all regions of Capillary beds are present in all regions of
the body but not all capillary beds are the body but not all capillary beds are
open at the same time. open at the same time.
Contraction of a Contraction of a sphinctersphincter musclemuscle closes closes
off a bed and blood can flow through an off a bed and blood can flow through an
arteriovenous shuntarteriovenous shunt that bypasses the that bypasses the
capillary bed.capillary bed.

6. Anatomy of a capillary bedAnatomy of a capillary bed

7. The VeinsThe Veins
VenulesVenules drain blood from capillaries, drain blood from capillaries,
then join to form then join to form veinsveins that take blood that take blood
to the heart. to the heart.
Veins have much less smooth muscle Veins have much less smooth muscle
and connective tissue than arteries. and connective tissue than arteries.
Veins often have Veins often have valvesvalves that prevent that prevent
the backward flow of blood when the backward flow of blood when
closed.closed.
Veins carry about 70% of the body’s Veins carry about 70% of the body’s
blood and act as a blood and act as a reservoirreservoir during during
hemorrhagehemorrhage..

8. The The heartheart is a cone-shaped, muscular is a cone-shaped, muscular
organ located between the lungs organ located between the lungs
behind the sternum.behind the sternum.
The heart muscle forms the The heart muscle forms the
myocardiummyocardium, with tightly interconnect , with tightly interconnect
cells of cells of cardiac musclecardiac muscle tissue. tissue.
The The pericardiumpericardium is the outer is the outer
membranous sac with lubricating fluid.membranous sac with lubricating fluid.
The HeartThe Heart

9. The heart has four chambers: two upper, The heart has four chambers: two upper,
thin-walled thin-walled atriaatria, and two lower, thick-, and two lower, thick-
walled walled ventriclesventricles..
The The septumseptum is a wall dividing the right is a wall dividing the right
and left sides. and left sides.
Atrioventricular valvesAtrioventricular valves occur between the occur between the
atria and ventricles – the atria and ventricles – the tricuspidtricuspid valvevalve
on the right and the on the right and the bicuspid valvebicuspid valve on the on the
left; both valves are reenforced by left; both valves are reenforced by
chordae tendinaechordae tendinae attached to muscular attached to muscular
projections within the ventricles.projections within the ventricles.

10. External heart anatomyExternal heart anatomy

11. Coronary artery circulationCoronary artery circulation

12. Passage of Blood Through Passage of Blood Through
the Heartthe Heart
Blood follows this sequence through the Blood follows this sequence through the
heart: superior and inferior vena cava heart: superior and inferior vena cava →→
right atrium right atrium tricuspid valve → → tricuspid valve → → right right
ventricle ventricle pulmonary semilunar valve → → pulmonary semilunar valve → →
pulmonary trunk and arteries to the lungs pulmonary trunk and arteries to the lungs
→→ pulmonary veins leaving the lungs pulmonary veins leaving the lungs →→ left left
atrium atrium bicuspid valve → → bicuspid valve → → left ventricle left ventricle → →
aortic semilunar valve →aortic semilunar valve → aorta aorta to the → to the →
bodybody. .

13. Internal view of the heartInternal view of the heart

14. The pumping of the heart sends out The pumping of the heart sends out
blood under pressure to the arteries.blood under pressure to the arteries.
Blood pressureBlood pressure is greatest in the is greatest in the
aorta; the wall of the left ventricle is aorta; the wall of the left ventricle is
thicker than that of the right ventricle thicker than that of the right ventricle
and pumps blood to the entire body.and pumps blood to the entire body.
Blood pressure then decreases as the Blood pressure then decreases as the
cross-sectional area of arteries and cross-sectional area of arteries and
then arterioles increases.then arterioles increases.

15. Path of blood through the heartPath of blood through the heart

16. The HeartbeatThe Heartbeat
Each heartbeat is called a Each heartbeat is called a cardiac cyclecardiac cycle..
When the heart beats, the two atria When the heart beats, the two atria
contract together, then the two contract together, then the two
ventricles contract; then the whole heart ventricles contract; then the whole heart
relaxes.relaxes.
SystoleSystole is the contraction of heart is the contraction of heart
chambers; chambers; diastolediastole is their relaxation. is their relaxation.
The The heart soundsheart sounds, lub-dup, are due to , lub-dup, are due to
the closing of the atrioventricular valves, the closing of the atrioventricular valves,
followed by the closing of the semilunar followed by the closing of the semilunar
valves.valves.

17. Intrinsic Control of HeartbeatIntrinsic Control of Heartbeat
The The SASA ((sinoatrialsinoatrial) ) nodenode, or , or pacemakerpacemaker, ,
initiates the heartbeat and causes the initiates the heartbeat and causes the
atria to contract on average every 0.85 atria to contract on average every 0.85
seconds. seconds.
The The AVAV ( (atrioventricularatrioventricular) ) nodenode conveys conveys
the stimulus and initiates contraction of the stimulus and initiates contraction of
the ventricles. the ventricles.
The signal for the ventricles to contract The signal for the ventricles to contract
travels from the AV node through the travels from the AV node through the
atrioventricular bundleatrioventricular bundle to the smaller to the smaller
Purkinje fibersPurkinje fibers..

18. Conduction system of the Conduction system of the
heartheart

19. Extrinsic Control of HeartbeatExtrinsic Control of Heartbeat
A A cardiac control centercardiac control center in the medulla in the medulla
oblongata speeds up or slows down the oblongata speeds up or slows down the
heart rate by way of the autonomic heart rate by way of the autonomic
nervous system branches: nervous system branches:
parasympathetic systemparasympathetic system (slows heart (slows heart
rate) and the rate) and the sympathetic systemsympathetic system
(increases heart rate). (increases heart rate).
Hormones Hormones epinephrineepinephrine and and
norepinephrinenorepinephrine from the adrenal from the adrenal
medulla also stimulate faster heart rate.medulla also stimulate faster heart rate.

20. The ElectrocardiogramThe Electrocardiogram
An An electrocardiogramelectrocardiogram ( (ECGECG) is a ) is a
recording of the electrical changes recording of the electrical changes
that occur in the myocardium during a that occur in the myocardium during a
cardiac cycle. cardiac cycle.
Atrial depolarizationAtrial depolarization creates the creates the P P
wavewave, , ventricle depolarizationventricle depolarization creates creates
the the QRS waveQRS wave, and , and repolarizationrepolarization of of
the ventricles produces the the ventricles produces the T waveT wave..

21. ElectrocardiogramElectrocardiogram

22. The Vascular PathwaysThe Vascular Pathways
The cardiovascular system includes The cardiovascular system includes
two circuits:two circuits:
2)2)Pulmonary circuitPulmonary circuit which circulates which circulates
blood through the lungs, andblood through the lungs, and
3)3)Systemic circuitSystemic circuit which circulates which circulates
blood to the rest of the body.blood to the rest of the body.
4)4)Both circuits are vital to homeostasis.Both circuits are vital to homeostasis.

23. Cardiovascular system diagramCardiovascular system diagram

24. The Pulmonary CircuitThe Pulmonary Circuit
The The pulmonary circuitpulmonary circuit begins with the begins with the
pulmonary trunkpulmonary trunk from the right ventricle from the right ventricle
which branches into two which branches into two pulmonary pulmonary
arteriesarteries that take oxygen-poor blood to that take oxygen-poor blood to
the lungs. the lungs.
In the lungs, oxygen diffuses into the In the lungs, oxygen diffuses into the
blood, and carbon dioxide diffuses out blood, and carbon dioxide diffuses out
of the blood to be expelled by the of the blood to be expelled by the
lungs.lungs.
Four Four pulmonary veinspulmonary veins return oxygen- return oxygen-
rich blood to the left atrium.rich blood to the left atrium.

25. The Systemic CircuitThe Systemic Circuit
The The systemic circuitsystemic circuit starts with the starts with the
aorta carrying Oaorta carrying O
22-rich blood from the -rich blood from the
left ventricle. left ventricle.
The aorta branches with an artery going The aorta branches with an artery going
to each specific organ. to each specific organ.
Generally, an artery divides into Generally, an artery divides into
arterioles and capillaries which then arterioles and capillaries which then
lead to venules. lead to venules.

26. The vein that takes blood to the vena cava The vein that takes blood to the vena cava
often has the same name as the artery often has the same name as the artery
that delivered blood to the organ.that delivered blood to the organ.
 In the adult systemic circuit, arteries In the adult systemic circuit, arteries
carry blood that is relatively high in carry blood that is relatively high in
oxygen and relatively low in carbon oxygen and relatively low in carbon
dioxide, and veins carry blood that is dioxide, and veins carry blood that is
relatively low in oxygen and relatively high relatively low in oxygen and relatively high
in carbon dioxide. in carbon dioxide.
This is the reverse of the pulmonary This is the reverse of the pulmonary
circuit.circuit.

27. Major arteries and veins of Major arteries and veins of
the systemic circuitthe systemic circuit

28. The The coronary arteriescoronary arteries serve the heart serve the heart
muscle itself; they are the first branch muscle itself; they are the first branch
off the aorta.off the aorta.
Since the coronary arteries are so Since the coronary arteries are so
small, they are easily clogged, leading small, they are easily clogged, leading
to heart disease.to heart disease.
The The hepatic portal systemhepatic portal system carries carries
blood rich in nutrients from digestion blood rich in nutrients from digestion
in the small intestine to the liver, the in the small intestine to the liver, the
organ that monitors the composition organ that monitors the composition
of the bloodof the blood..

29. Blood FlowBlood Flow
The beating of the heart is necessary The beating of the heart is necessary
to homeostasis because it creates to homeostasis because it creates
pressure that propels blood in arteries pressure that propels blood in arteries
and the arterioles.and the arterioles.
Arterioles lead to the capillaries where Arterioles lead to the capillaries where
nutrient and gas exchange with tissue nutrient and gas exchange with tissue
fluid takes place.fluid takes place.

30. Blood Flow in ArteriesBlood Flow in Arteries
Blood pressureBlood pressure due to the pumping of due to the pumping of
the heart accounts for the flow of blood the heart accounts for the flow of blood
in the arteries. in the arteries.
Systolic pressureSystolic pressure is high when the heart is high when the heart
expels the blood. expels the blood.
Diastolic pressureDiastolic pressure occurs when the heart occurs when the heart
ventricles are relaxing. ventricles are relaxing.
Both pressures decrease with distance Both pressures decrease with distance
from the left ventricle because blood from the left ventricle because blood
enters more and more arterioles and enters more and more arterioles and
arteries.arteries.

31. Cross-sectional area as it relates to Cross-sectional area as it relates to
blood pressure and velocityblood pressure and velocity

32. Blood Flow in CapillariesBlood Flow in Capillaries
Blood moves slowly in capillaries Blood moves slowly in capillaries
because there are more capillaries because there are more capillaries
than arterioles. than arterioles.
This allows time for substances to be This allows time for substances to be
exchanged between the blood and exchanged between the blood and
tissues.tissues.

33. Blood Flow in VeinsBlood Flow in Veins
Venous blood flow is dependent upon:Venous blood flow is dependent upon:
2)2)skeletal muscle contraction, skeletal muscle contraction,
3)3)presence of valves in veins, and presence of valves in veins, and
4)4)respiratory movements. respiratory movements.
Compression of veins causes blood to Compression of veins causes blood to
move forward past a valve that then move forward past a valve that then
prevents it from returning backward. prevents it from returning backward.

34. Changes in thoracic and abdominal Changes in thoracic and abdominal
pressure that occur with breathing also pressure that occur with breathing also
assist in the return of blood. assist in the return of blood.
Varicose veinsVaricose veins develop when the valves of develop when the valves of
veins become weak. veins become weak.
HemorrhoidsHemorrhoids (piles) are due to varicose (piles) are due to varicose
veins in the rectum. veins in the rectum.
PhlebitisPhlebitis is inflammation of a vein and can is inflammation of a vein and can
lead to a blood clot and possible death if lead to a blood clot and possible death if
the clot is dislodged and is carried to a the clot is dislodged and is carried to a
pulmonary vessel.pulmonary vessel.

35. BloodBlood
Blood separates into two main parts: Blood separates into two main parts: plasmaplasma
and and formed elementsformed elements. .
Plasma accounts for 55% and formed Plasma accounts for 55% and formed
elements 45% of blood volume.elements 45% of blood volume.
Plasma contains mostly water (90–92%) and Plasma contains mostly water (90–92%) and
plasma proteins (7–8%), but it also contains plasma proteins (7–8%), but it also contains
nutrients and wastes. nutrients and wastes.
AlbuminAlbumin is a large plasma protein that is a large plasma protein that
transports bilirubin; transports bilirubin; globulinsglobulins are plasma are plasma
proteins that proteins that transporttransport lipoproteins. lipoproteins.

36. Composition of bloodComposition of blood

37. The Red Blood CellsThe Red Blood Cells
Red blood cellsRed blood cells ((erythrocytes erythrocytes oror RBCs RBCs) are ) are
made in the made in the red bone marrowred bone marrow of the skull, of the skull,
ribs, vertebrae, and the ends of long ribs, vertebrae, and the ends of long
bones.bones.
Normally there are 4 to 6 million RBCs per Normally there are 4 to 6 million RBCs per
mmmm
33
of whole blood. of whole blood.
Red blood cells contain the pigment Red blood cells contain the pigment
hemoglobinhemoglobin for oxygen transport; for oxygen transport;
hemogobin contains hemogobin contains hemeheme, a complex iron-, a complex iron-
containing group that transports oxygen in containing group that transports oxygen in
the blood. the blood.

38. Physiology of red blood cellsPhysiology of red blood cells

39. The air pollutant The air pollutant carbon monoxidecarbon monoxide
combines more readily with combines more readily with
hemoglobin than does oxygen, hemoglobin than does oxygen,
resulting in oxygen deprivation and resulting in oxygen deprivation and
possible death.possible death.
Red blood cells lack a nucleus and Red blood cells lack a nucleus and
have a 120 day life span. have a 120 day life span.
When worn out, the red blood cells When worn out, the red blood cells
are dismantled in the liver and spleen. are dismantled in the liver and spleen.

40. Iron is reused by the red bone marrow Iron is reused by the red bone marrow
where stem cells continually produce more where stem cells continually produce more
red blood cells; the remainder of the heme red blood cells; the remainder of the heme
portion undergoes chemical degradation portion undergoes chemical degradation
and is excreted as bile pigments into the and is excreted as bile pigments into the
bile. bile.
Lack of enough hemoglobin results in Lack of enough hemoglobin results in
anemiaanemia. .
The kidneys produce the hormone The kidneys produce the hormone
erythropoietinerythropoietin to increase blood cell to increase blood cell
production when oxygen levels are low.production when oxygen levels are low.

41. The White Blood CellsThe White Blood Cells
White blood cellsWhite blood cells ( (leukocytesleukocytes) have nuclei, ) have nuclei,
are fewer in number than RBCs, with are fewer in number than RBCs, with
5,000 – 10,000 cells per mm5,000 – 10,000 cells per mm
33
, and defend , and defend
against disease. against disease.
Leukocytes are divided into Leukocytes are divided into granulargranular and and
agranularagranular based on appearance. based on appearance.
Granular leukocytes (Granular leukocytes (neutrophilsneutrophils, ,
eosinophilseosinophils, and , and basophilsbasophils) contain ) contain
enzymes and proteins that defend the enzymes and proteins that defend the
body against microbes.body against microbes.

42. The aganular leukocytes (The aganular leukocytes (monocytesmonocytes and and
lymphocyteslymphocytes) have a spherical or kidney-) have a spherical or kidney-
shaped nucleus.shaped nucleus.
Monocytes can differentiate into Monocytes can differentiate into
macrophagesmacrophages that that phagocytizephagocytize microbes microbes
and stimulate other cells to defend the and stimulate other cells to defend the
body.body.
Lymphocytes are involved in immunity.Lymphocytes are involved in immunity.
An excessive number of white blood cells An excessive number of white blood cells
may indicate an infection or may indicate an infection or leukemialeukemia; HIV ; HIV
infection drastically reduces the number of infection drastically reduces the number of
lymphocytes.lymphocytes.

43. Macrophage engulfing bacteriaMacrophage engulfing bacteria

44. The Platelets and Blood The Platelets and Blood
ClottingClotting
Red bone marrow produces large cells Red bone marrow produces large cells
called called megakaryocytesmegakaryocytes that fragment into that fragment into
plateletsplatelets at a rate of 200 billion per day; at a rate of 200 billion per day;
blood contains 150,000–300,000 platelets blood contains 150,000–300,000 platelets
per mmper mm
33
. .
Twelve Twelve clotting factorsclotting factors in the blood help in the blood help
platelets form blood clots.platelets form blood clots.

45. Blood ClottingBlood Clotting
Injured tissues release a clotting factor Injured tissues release a clotting factor
called called prothrombin activatorprothrombin activator, which , which
converts prothrombin into thrombin.converts prothrombin into thrombin.
Thrombin, in turn, acts as an enzyme and Thrombin, in turn, acts as an enzyme and
converts fibrinogen into insoluble threads converts fibrinogen into insoluble threads
of of fibrinfibrin..
These conversions require the presence of These conversions require the presence of
calcium ions (Cacalcium ions (Ca
2+2+
).).
Trapped red blood cells make a clot Trapped red blood cells make a clot
appear red. appear red.

46. Blood clottingBlood clotting

47. HemophiliaHemophilia
HemophiliaHemophilia is an inherited clotting disorder is an inherited clotting disorder
due to a deficiency in a clotting factor.due to a deficiency in a clotting factor.
Bumps and falls cause bleeding in the Bumps and falls cause bleeding in the
joints; cartilage degeneration and joints; cartilage degeneration and
resorption of bone can follow.resorption of bone can follow.
The most frequent cause of death is The most frequent cause of death is
bleeding into the brain with accompanying bleeding into the brain with accompanying
neurological damage.neurological damage.

48. Bone Marrow Stem CellsBone Marrow Stem Cells
A A stem cellstem cell is capable of dividing into is capable of dividing into
new cells that differentiate into new cells that differentiate into
particular cell types.particular cell types.
Bone marrow is Bone marrow is multipotentmultipotent, able to , able to
continually give rise to particular types continually give rise to particular types
of blood cells. of blood cells.
The skin and brain also have stem cells, The skin and brain also have stem cells,
and and mesenchymal stem cellsmesenchymal stem cells give rise to give rise to
connective tissues including heart connective tissues including heart
musclemuscle. .

49. Blood cell formation in red Blood cell formation in red
bone marrowbone marrow

50. Capillary ExchangeCapillary Exchange
At the arteriole end of a capillary, water At the arteriole end of a capillary, water
moves out of the blood due to the force of moves out of the blood due to the force of
blood pressureblood pressure. .
At the venule end, water moves into the At the venule end, water moves into the
blood due to blood due to osmotic pressureosmotic pressure of the of the
blood.blood.
Substances that leave the blood contribute Substances that leave the blood contribute
to to tissue fluidtissue fluid, the fluid between the , the fluid between the
body’s cells.body’s cells.

51. In the midsection of the capillary, In the midsection of the capillary,
nutrients diffuse out and wastes diffuse nutrients diffuse out and wastes diffuse
into the blood. into the blood.
Since plasma proteins are too large to Since plasma proteins are too large to
readily pass out of the capillary, tissue readily pass out of the capillary, tissue
fluid tends to contain all components of fluid tends to contain all components of
plasma except it has lesser amounts of plasma except it has lesser amounts of
protein.protein.
Excess tissue fluid is returned to the blood Excess tissue fluid is returned to the blood
stream as stream as lymphlymph in in lymphatic vesselslymphatic vessels..

52. Capillary exchangeCapillary exchange

53. Cardiovascular DisordersCardiovascular Disorders
Cardiovascular diseaseCardiovascular disease ( (CVDCVD) is the ) is the
leading cause of death in Western leading cause of death in Western
countries.countries.
Modern research efforts have improved Modern research efforts have improved
diagnosis, treatment, and prevention.diagnosis, treatment, and prevention.
Major cardiovascular disorders include Major cardiovascular disorders include
atherosclerosis, stroke, heart attack, atherosclerosis, stroke, heart attack,
aneurysm, and hypertension.aneurysm, and hypertension.

54. AtherosclerosisAtherosclerosis
AtherosclerosisAtherosclerosis is due to a build-up of is due to a build-up of
fatty material (fatty material (plaqueplaque), mainly ), mainly
cholesterol, under the inner lining of cholesterol, under the inner lining of
arteries. arteries.
The plaque can cause a The plaque can cause a thrombusthrombus (blood (blood
clot) to form.clot) to form.
The thrombus can dislodge as an The thrombus can dislodge as an embolusembolus
and lead to and lead to thromboembolismthromboembolism..

55. Stroke, Heart Attack, and Stroke, Heart Attack, and
AneurysmAneurysm
A A cerebrovascular accidentcerebrovascular accident, or , or strokestroke, ,
results when an embolus lodges in a results when an embolus lodges in a
cerebral blood vessel or a cerebral blood cerebral blood vessel or a cerebral blood
vessel bursts; a portion of the brain dies vessel bursts; a portion of the brain dies
due to lack of oxygen. due to lack of oxygen.
A A myocardial infarctionmyocardial infarction, or , or heart attackheart attack, ,
occurs when a portion of heart muscle occurs when a portion of heart muscle
dies due to lack of oxygen.dies due to lack of oxygen.

56. Partial blockage of a coronary artery Partial blockage of a coronary artery
causes causes angina pectorisangina pectoris, or chest pain. , or chest pain.
An An aneurysmaneurysm is a ballooning of a blood is a ballooning of a blood
vessel, usually in the abdominal aorta or vessel, usually in the abdominal aorta or
arteries leading to the brain.arteries leading to the brain.
Death results if the aneurysm is in a large Death results if the aneurysm is in a large
vessel and the vessel bursts.vessel and the vessel bursts.
Atherosclerosis and hypertension weaken Atherosclerosis and hypertension weaken
blood vessels over time, increasing the blood vessels over time, increasing the
risk of aneurysm.risk of aneurysm.

57. Coronary Bypass OperationsCoronary Bypass Operations
A A coronary bypass operationcoronary bypass operation involves involves
removing a segment of another blood removing a segment of another blood
vessel and replacing a clogged coronary vessel and replacing a clogged coronary
artery. artery.
It may be possible to replace this It may be possible to replace this
surgery with surgery with gene therapygene therapy that that
stimulates new blood vessels to grow stimulates new blood vessels to grow
where the heart needs more blood flow. where the heart needs more blood flow.

58. Coronary bypass operationCoronary bypass operation

59. Clearing Clogged ArteriesClearing Clogged Arteries
AngioplastyAngioplasty uses a long tube threaded uses a long tube threaded
through an arm or leg vessel to the through an arm or leg vessel to the
point where the coronary artery is point where the coronary artery is
blocked; inflating the tube forces the blocked; inflating the tube forces the
vessel open. vessel open.
Small metal Small metal stentsstents are expanded inside are expanded inside
the artery to keep it open.the artery to keep it open.
Stents are coated with Stents are coated with heparinheparin to to
prevent blood clotting and with prevent blood clotting and with
chemicals to prevent arterial closing.chemicals to prevent arterial closing.

60. AngioplastyAngioplasty

61. Dissolving Blood ClotsDissolving Blood Clots
Medical treatments for dissolving blood Medical treatments for dissolving blood
clots include use of clots include use of t-PAt-PA ( (tissue tissue
plasminogen activatorplasminogen activator) that converts ) that converts
plasminogen into plasmin, an enzyme that plasminogen into plasmin, an enzyme that
dissolves blood clots, but can cause brain dissolves blood clots, but can cause brain
bleeding. bleeding.
AspirinAspirin reduces the stickiness of platelets reduces the stickiness of platelets
and reduces clot formation and lowers the and reduces clot formation and lowers the
risk of heart attack.risk of heart attack.

62. Heart Transplants and Artificial Heart Transplants and Artificial
HeartsHearts
Heart transplantsHeart transplants are routinely are routinely
performed but immunosuppressive drugs performed but immunosuppressive drugs
must be taken thereafter. must be taken thereafter.
There is a shortage of human organ There is a shortage of human organ
donors. donors.
Work is currently underway to improve Work is currently underway to improve
self-contained self-contained artificial heartsartificial hearts, and , and
muscle cell transplants may someday be muscle cell transplants may someday be
usefuluseful..

63. HypertensionHypertension
About 20% of Americans suffer from About 20% of Americans suffer from
hypertensionhypertension ( (high blood pressurehigh blood pressure).).
Hypertension is present when systolic Hypertension is present when systolic
pressure is 140 or greater or diastolic pressure is 140 or greater or diastolic
pressure is 100 or greater; diastolic pressure pressure is 100 or greater; diastolic pressure
is emphasized when medical treatment is is emphasized when medical treatment is
considered.considered.
A genetic predisposition for hypertension A genetic predisposition for hypertension
occurs in those who have a gene that codes occurs in those who have a gene that codes
for for angiotensinogenangiotensinogen, a powerful , a powerful
vasoconstrictor.vasoconstrictor.